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 gsmith September 27, 2013 13:50

CFX Momentum Inputs Question

Hi all!

I am new to using CFX and a novice with CFD analysis. I'm working on a problem with a moving tank. To simulate the movement of the tank in the fluid, I am trying to input momentum source information. The momentum info I am using was calculated from Reynolds Transport. However, for a general Reynolds Transport in Momentum, the units come out to be kg*m/s. The CFX Momentum input asks for a momentum source coefficient with units kg/(m^3 s) and a vector with units kg/(m^2 s^2). How do I go from a general momentum case to the needed values/equations for the CFX momentum input?

Thank you,

G. Smith

 evcelica September 27, 2013 17:09

Don't use the momentum source coefficient. That is for making it a function of velocity.
Just use the Component option, which has units of kg/(m^2 s^2) = momentum per unit volume per second = (kg*m/s) / (m^3 s)

 gsmith October 21, 2013 10:46

Thank you for the reply!
The per unit volume makes sense if I divide the general momentum case by the total fluid volume. But I still don't understand how to go from general momentum to the per time. Is the general momentum divided by the timestep? or by the overall time of the run?

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